/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/DynamicMesh3.h
Compute a normal/tangent frame at vertex that is "stable" as long as the mesh topology doesn't change, meaning that one axis of the frame will be computed from projection of outgoing edge.Bydefault, frame.Z is normal, and .X points along mesh edge. Requires that VertexNormals are available, or UseNormal != nullptr, otherwise returns default Frame3d
[FFrame3d](API\Runtime\GeometryCore\FFrame3d_1) GetVertexFrame ( int VertexID, bool bFrameNormalY, FVector3d * UseNormal ) const